Randolph H. Hastings

Cervical Spine Movement during Laryngoscopy with the Bullard, Macintosh, and Miller Laryngoscopes

BACKGROUND: Direct laryngoscopy requires movement of the head, neck, and cervical spine. Spine movement may be limited for anatomic reasons or because of cervical spine injury. The Bullard laryngoscope, a rigid fiberoptic laryngoscope, may cause less neck flexion and head extension than conventional laryngoscopes. The purpose of this study was to compare head extension (measured externally), cervical spine extension (measured radiographically), and laryngeal view obtained with the Bullard, Macintosh, and Miller laryngoscopes. METHODS: Anesthesia was induced in 35 ASA 1-3 elective surgery patients. Patients lay on a rigid board with head in neutral position. Laryngoscopy was performed three times, changing between the Bullard, Macintosh, and Miller laryngoscopes. Head extension was measured with an angle finder attached to goggles worn by the patient. The best laryngeal view with each laryngoscope was assessed by the laryngoscopist. In eight patients, lateral cervical spine radiographs were taken before and during laryngoscopy with the Bullard and Macintosh blades. RESULTS: Median values for external head extension were 11 degrees, 10 degrees, and 2 degrees with the Macintosh, Miller, and Bullard laryngoscopy (P < 0.01), respectively. Significant reductions in radiographic cervical spine extension were found for the Bullard compared to the Macintosh blade at the atlantooccipital joint, atlantoaxial joint, and C3-C4. Median atlantooccipital extension angles were 6 degrees and 12 degrees for the Bullard and Macintosh laryngoscopes, respectively. The larynx could be exposed in all patients with the Bullard but only in 90% with conventional laryngoscope (P < 0.01). CONCLUSIONS: The Bullard laryngoscope caused less head extension and cervical spine extension than conventional laryngoscopes and resulted in a better view. It may be useful in care of patients in whom cervical spine movement is limited or undesirable.

Airway management for trauma patients with potential cervical spine injuries

nesthesiologists are often involved in the initial resuscitation and management of trauma A victims with possible cenrical spine injuries. They should recognize the situations in which such injuries are likely, be familiar with evaluation of the cervical spine, and understand the risks and benefits of alternative approaches to airway management. Crosby and Lui (1) recently published for the anesthetist an excellent review of the anatomy, biomechanics, and disease processes affecting the cervical spine. In this article, we review the mechanisms of traumatic cervical spine injury, physical and radiologic examination, and methods for initially stabilizing the injured spine, and we focus on airway management and tracheal intubation techniques. There are no guidelines for choice of tracheal intubation technique based on the clinical situation. Different authors recommend awake tracheal intubation ( 2 4 , direct laryngoscopy with head and neck stabilization (3,7,8), or cricothyroidotomy (3,4,9,10), but none consider whether a particular technique may be either appropriate or contraindicated in some circumstances. Crosby and Lui suggest that the method is generally unimportant as long as a cervical spine injury is recognized and reasonable care is taken with tracheal intubation. However, the risks and benefits of various approaches may vary according to the circumstances of specific cases. We review the advantages and disadvantages of alternative methods of establishing an airway in patients with actual or potential cervical spine trauma and propose that anesthesiologists develop a case-specific strategy for airway management.

Head extension and laryngeal view during laryngoscopy with cervical spine stabilization maneuvers.

Background:Direct laryngoscopy frequently is modified in patients with known or suspected cervical spine injury. The goals of this study were to measure the degrees of head extension required to expose the arytenoid cartilages and glottis if neck flexion were not possible and to determine whether in-line stabilization maneuvers alter the amount of head extension. Methods:The subjects were anesthetized patients with normal cervical spines and Mallampati class 1 oropharyngeal views. Head extension was measured relative to a line drawn perpendicular to the table. Stabilization consisted of either passive immobilization, with the head held flat against a rigid board, or axial traction. Results:Without stabilization, arytenoid cartilage exposure and the best view of the glottis was achieved with a 10 ± 5° (mean ± SD) head extension and a 15 ± 6° head extension, respectively (n=31). Head immobilization reduced extension angles 4 ± 5° for arytenoid exposure and 5 ± 6° for best view compared with no stabilization. Conclusions:Head immobilization reduced head extension necessary for laryngoscopy. If head extension is construed to be potentially dangerous in patients with cervical spine injuries, head immobilization without traction might be the preferable stabilization technique.

Force and torque vary between laryngoscopists and laryngoscope blades

Several studies have examined the effects of patient characteristics on force of laryngoscopy, but little attention has been paid to the importance of technique and equipment.This study investigated whether force, torque, head extension, and view varied significantly between laryngoscopists and compared force and torque using Macintosh 3 and Miller 2 blades. The study population consisted of ASA grade I and II patients requiring general anesthesia and endotracheal intubation for elective surgery. Force, torque, head extension, and laryngeal view were highly reproducible when laryngoscopy was repeated by the same individual. Force and torque showed great variation between laryngoscopies performed by different anesthetists. For example, peak force varied over a range of 56 newtons among patients, but could also vary as much as 30 newtons between different anesthetists repeating laryngoscopy in the same patient. Force and head extension were 30% less with the Miller laryngoscope compared to the Macintosh. Thus, laryngoscopic force and torque depend on technique and equipment. Further studies of force and torque may lead to improved techniques. The force-measuring laryngoscope could be a useful tool in teaching laryngoscopy. (Anesth Analg 1996;82:462-8)

Force, torque, and stress relaxation with direct laryngoscopy.

The anesthetist exerts axial force on the laryngoscope handle to expose the glottis.The anesthetist must also apply a perpendicular force to balance the torque on the laryngoscope. Several studies have measured axial force during direct laryngoscopy, but none has measured torque. This study used a newly designed laryngoscope handle to measure force and torque simultaneously during direct laryngoscopy of ASA grade I and II patients requiring general anesthesia and endotracheal intubation for elective surgery. In 58 patients, peak force averaged 38 +/- 2 newtons. Peak torque averaged 4 +/- 0.2 newton-meters, and the perpendicular force was estimated as 40 +/- 2 newtons. The peak torque that can be balanced by the wrist is approximately 6 newton-meters, suggesting that torque may be a limiting factor for laryngoscopy in some situations. Peak force and torque demonstrated stress relaxation, a viscous property of biologic tissues. Force and torque decreased monoexponentially to approximately 70% of peak values with a half-time of 4 +/- 0.3 s. The phenomenon occurred in spite of administration of muscle relaxants, and was probably due to stress relaxation of pharyngeal tissues that are passively stretched during laryngoscopy. (Anesth Analg 1996;82:456-61)

The callander laryngoscope blade modification is associated with a decreased risk of dental contact

PurposeDental damage may occur with laryngoscopy. The purpose of this study was twofold : to determine whether preoperative examination could predict the risk of contacting the teeth with the laryngoscope and to evaluate the effectiveness of a modified Macintosh blade on reducing dental contact.MethodsFour hundred and eighty-three patients scheduled for elective surgery requiring general anesthesia with endotracheal tube placement were studied prospectively. Features that might predict difficult intubation were assessed preoperatively. Laryngoscopy was performed twice on each patient, once with a regular Macintosh 3 blade and once with a blade in which the flange was partially removed (Callander modification). The distance between the flange of the blade and the upper incisors at glottic exposure was measured. We calculated correlations between individual airway characteristics and the chance of hitting the upper teeth with the regular Macintosh 3 blade and compared the frequencies of contacting the teeth between the two blades.ResultsThe chance of hitting the upper teeth when using the regular Macintosh 3 blade increased significantly with non-parametric scores for Mallampati classification, mandibular subluxation, head and neck movement, interincisor gap, and condition of the upper teeth. (P < 0.01) The frequency of direct contact varied significantly between the two blades: 20.3% vs 4.1% for Macintosh 3 and modified blades, respectively (P < 0.05). Laryngeal views were improved with the modified blade.ConclusionAirway characteristics correlate with the risk of hitting the upper teeth during laryngoscopy. The modified Macintosh blade reduces the risk of contacting the teeth.RésuméObjectifLa laryngoscopie peut provoquer des lésions aux dents. Notre double objectif était : de déterminer si l’examen préopératoire peut permettre de prédire le risque de toucher les dents avec le laryngoscope et d’évaluer l’efficacité d’une lame Macintosh modifiée sur la réduction de contact avec les dents.MéthodeDes patients (483) devant subir une intervention chirurgicale réglée nécessitant une anesthésie générale avec la mise en place d’un tube endotrachéal ont participé à notre étude prospective. Nous avons fait l’évaluation préopératoire des caractéristiques permettant de prédire une intubation difficile. La laryngoscopie a été réalisée deux fois sur chaque patient, avec une lame Macintosh 3 ordinaire et avec une lame dont le connecteur à bride avait été partiellement enlevé (modification Callander). La distance entre le manche de la lame et les incisives supérieures a été mesurée à l’exposition de la glotte. Nous avons calculé les corrélations entre les caractéristiques individuelles des voies aériennes et le risque de toucher les dents supérieures avec la lame Macintosh 3 ordinaire, et comparé les fréquences de contact avec les dents pour les deux lames.RésultatsLe risque de toucher les dents supérieures avec la lame Macintosh 3 ordinaire augmente significativement avec les scores non-paramétriques de la classification de Mallampati, la subluxation mandibulaire, le mouvement de la tête et du cou, l’espace inter-incisive et l’état de la dentition supérieure (P < 0,01). La fréquence de contact direct varie significativement d’une lame à l’autre : 20,3 % vs 41% respectivement pour la lame Macintosh 3 et la lame modifiée (P < 0,05). Les visualisations du larynx sont meilleures avec la lame modifiée.ConclusionIl existe une corrélation entre les caractéristiques des voies aériennes et le risque de toucher les dents supérieures pendant la laryngoscopie. La lame Macintosh modifiée réduit ce risque.

The Bisphosphonate Olpadronate Inhibits Skeletal Prostate Cancer Progression in a Green Fluorescent Protein Nude Mouse Model

Purpose: Metastatic bone disease is one of the major causes of morbidity and mortality in prostate cancer patients. Bisphosphonates are currently used to inhibit bone resorption and reduce tumor-induced skeletal complications. More effective bisphosphonates would enhance their clinical value. Experimental Design: We tested several bisphosphonates in a green fluorescent protein (GFP)–expressing human prostate cancer nude mouse model. The in vivo effects of four bisphosphonates, including pamidronate, etidronic acid, and olpadronate, on bone tumor burden in mice intratibially inoculated with PC-3-GFP human prostate cancer cells were visualized by whole-body fluorescence imaging and X-ray. Results: The PC-3-GFP cells produced extensive bone lesions when injected into the tibia of immunocompromised mice. The skeletal progression of the PC-3-GFP cell growth was monitored by GFP fluorescence and the bone destruction was evaluated by X-ray. We showed that 3,3-dimethylaminopropane-1-hydroxy-1,1-diphosphonic acid (olpadronate) was the most effective bisphosphonate treatment in reducing tumor burden as assessed by GFP imaging and radiography. The GFP tumor area and X-ray score significantly correlated. Reduced tumor growth in the bone was accompanied by reduced serum calcium, parathyroid hormone–related protein, and osteoprotegerin. Conclusions: The serum calcium, parathyroid hormone–related protein, and osteoprotegerin levels were significantly correlated with GFP area and X-ray scores. Treatment with olpadronate reduced tumor growth in the bone measured by GFP and X-ray imaging procedures. Imaging of GFP expression enables monitoring of tumor growth in the bone and the GFP results complement the X-ray assessment of bone disease. The data in this report suggest that olpadronate has potential as an effective inhibitor of the skeletal progression of clinical prostate cancer.

Parathyroid hormone‐related protein regulates the growth of orthotopic human lung tumors in athymic mice

Parathyroid hormone‐related protein (PTHrP) has growth regulatory effects for many malignant cells and may influence the progression of carcinomas of the breast, prostate, and lung. In the current study, the authors investigated the in vivo and in vitro effects of PTHrP neutralizing antibody and PTHrP treatment on the growth of BEN cells, a human lung squamous cell carcinoma line that expresses PTHrP and its receptor.

Parathyroid hormone-related protein and lung biology.

Parathyroid hormone-related protein (PTHrP) is expressed in normal and malignant lung and has roles in development, homeostasis, and pathophysiology of injury and cancer. Its effects in developing lung include regulation of branching morphogenesis and type II cell maturation. In adult lung, PTHrP stimulates disaturated phosphatidylcholine secretion, inhibits type II cell growth, and sensitizes them to apoptosis. In lung cancer, PTHrP may play a role in carcinoma progression, or metastasis. The protein could be a useful marker for assessing lung maturity or type II cell function, predicting risk of injury, and detecting lung cancer. PTHrP-based therapies could also prove useful in lung injury and lung cancer.

Parathyroid Hormone-Related Protein in Tracheal Aspirates of Newborn Infants

PTH-related protein (PTHrP) is found with its receptor in a variety of normal mammalian embryonic tissues where it apparently regulates cellular growth and differentiation. PTHrP stimulates phosphatidylcholine synthesis in rat fetal lung explants, suggesting a role in fetal type II alveolar maturation and surfactant production. We investigated PTHrP levels in tracheal aspirates of newborn infants. We collected tracheal aspirates from 40 intubated newborn infants within the first 24 h of life. PTHrP levels were measured by a RIA using rabbit antisera to PTHrP peptide 38-64. We found significantly lower PTHrP levels in tracheal aspirates from infants born at less than 35 wk of gestation (p = 0.02) and with a birth weight less than 2 kg (p = 0.04). We also found significantly lower PTHrP levels in male preterm (<35 wk of gestation) infants compared with female infants(p = 0.01), and in preterm infants who required multiple doses of surfactant (p = 0.005). Preterm infants exposed to antenatal steroids had significantly higher levels of PTHrP in tracheal aspirates(p = 0.02). PTHrP is associated with various indices of lung maturation and may prove to be a mediator of differentiation and growth.